(i) Field of the Invention
The present invention relates to 3,4-trans-4-ethyl-1-(substituted phenyl)-3-(substituted phenyl)pyrrolidin-2-ones, a method for preparing the same, and herbicidal compositions for paddy fields containing the same as herbicidally active ingredients.
(ii) Description of the Prior Art
It has already been disclosed that certain kinds of pyrrolidin-2-one derivatives have a herbicidal activity, and the description regarding this fact is made in U.S. Pat. Nos. 4,110,105, 4,210,589 and 4,874,422, E.P. Publication No. 387,869 and the like. Furthermore, 3-chloro-4-chloromethyl-1-(3-trifluoromethylphenyl)-2-pyrrolidinone (general name fluorochloridone) which is a typical compound in these publications is commercially available. Additionally, also in U.S. Pat. No. 4,960,457, pyrrolidinone derivatives and herbicidal compositions are disclosed.
When utilized as herbicidal compositions, compounds disclosed in the above-mentioned U.S. Pat. Nos. 4,110,105, 4,210,589 and 4,874,422 are required to be used in a relatively large amount, i.e., in a relatively high application rate. In particular, when these compounds are used in paddy fields, there is the problem that they have a pharmaceutically injurious action on rice plants which are useful crops.
Moreover, compounds disclosed in examples of E.P. Publication No. 387,869 or U.S. Pat. No. 4,960,457 have the problem that an effect to weeds in a growing period is low, when they are used in paddy fields.
Heretofore, there has not been known any method for selectively and effectivel.y preparing preferable isomers of these pyrrolidinone derivatives which have a herbicidal activity, i.e., 3,4-trans isomers. Therefore, it has been very difficult to apply these compounds as practical herbicidal compositions.